The Batch Process of AGRIFURANE

The raw material is mixed with the filtrate of a belt filter press dewatering the residue. This leads to a slurry having a solid-to-liquid ratio of 1 6 by weight. 

The first reactor gets a mixture of primary and secondary steam to attain 177 °C (9.35 bar). The vapor from this first reactor is fed into the second reactor, but in addition to this vapor, the second reactor also gets some primary steam to partially make up for the pressure loss in the first reactor. Analogously, the vapor from the second reactor is fed into the third reactor, and so forth. As there must be a pressure drop from reactor to reactor to ascertain flow, the last reactor has only 161 °C (6.34 bar), but by an intricate pipe and valve system the batch period is split up in such a way that each reactor is run at each of the different temperatures for an equal interval of time, so that each charge is treated equally. 

The latest AGRIFURANE process uses sulfuric acid to give 1 % of this catalyst in the liquid portion of the charge, but the consumption of this acid is greatly reduced by the fact that in dewatering the residue by a belt filter press most of the acid is recovered in the filtrate, and this filtrate is recycled to be mixed with the incoming raw material to form the slurry mentioned above. 

The idea behind using a slurry rather than loose raw material was to permit processing fines, and the reason for running the reactors in series was obviously the desire to reduce the steam consumption. Nevertheless, the AGRIFURANE process has serious disadvantages  

Because of its high cost of investment, this process may be considered as obsolete. 

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